clk: clk-mux: implement remuxing on set_rate

Implement clk-mux remuxing if the CLK_SET_RATE_NO_REPARENT flag isn't
set. This implements determine_rate for clk-mux to propagate to each
parent and to choose the best one (like clk-divider this chooses the
parent which provides the fastest rate <= the requested rate).

The determine_rate op is implemented as a core helper function so that
it can be easily used by more complex clocks which incorporate muxes.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Mike Turquette <mturquette@linaro.org>

diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c
index b918dc3..0811633 100644 (file)
--- a/drivers/clk/clk-mux.c
+++ b/drivers/clk/clk-mux.c
@@ -104,6 +104,7 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
 const struct clk_ops clk_mux_ops = {
        .get_parent = clk_mux_get_parent,
        .set_parent = clk_mux_set_parent,
+       .determine_rate = __clk_mux_determine_rate,
 };
 EXPORT_SYMBOL_GPL(clk_mux_ops);
 

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f33f1cc..bc02037 100644 (file)
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -692,6 +692,55 @@ struct clk *__clk_lookup(const char *name)
        return NULL;
 }
 
+/*
+ * Helper for finding best parent to provide a given frequency. This can be used
+ * directly as a determine_rate callback (e.g. for a mux), or from a more
+ * complex clock that may combine a mux with other operations.
+ */
+long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
+                             unsigned long *best_parent_rate,
+                             struct clk **best_parent_p)
+{
+       struct clk *clk = hw->clk, *parent, *best_parent = NULL;
+       int i, num_parents;
+       unsigned long parent_rate, best = 0;
+
+       /* if NO_REPARENT flag set, pass through to current parent */
+       if (clk->flags & CLK_SET_RATE_NO_REPARENT) {
+               parent = clk->parent;
+               if (clk->flags & CLK_SET_RATE_PARENT)
+                       best = __clk_round_rate(parent, rate);
+               else if (parent)
+                       best = __clk_get_rate(parent);
+               else
+                       best = __clk_get_rate(clk);
+               goto out;
+       }
+
+       /* find the parent that can provide the fastest rate <= rate */
+       num_parents = clk->num_parents;
+       for (i = 0; i < num_parents; i++) {
+               parent = clk_get_parent_by_index(clk, i);
+               if (!parent)
+                       continue;
+               if (clk->flags & CLK_SET_RATE_PARENT)
+                       parent_rate = __clk_round_rate(parent, rate);
+               else
+                       parent_rate = __clk_get_rate(parent);
+               if (parent_rate <= rate && parent_rate > best) {
+                       best_parent = parent;
+                       best = parent_rate;
+               }
+       }
+
+out:
+       if (best_parent)
+               *best_parent_p = best_parent;
+       *best_parent_rate = best;
+
+       return best;
+}
+
 /***        clk api        ***/
 
 void __clk_unprepare(struct clk *clk)

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 5c0bc39..1f0285b 100644 (file)
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -436,6 +436,9 @@ unsigned long __clk_get_flags(struct clk *clk);
 bool __clk_is_prepared(struct clk *clk);
 bool __clk_is_enabled(struct clk *clk);
 struct clk *__clk_lookup(const char *name);
+long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
+                             unsigned long *best_parent_rate,
+                             struct clk **best_parent_p);
 
 /*
  * FIXME clock api without lock protection